The problem with humans and other mammals, at least from a genetic diagnostic perspective, is that they are diploid. Mutations in one allele, such as those responsible for all dominantly inherited syndromes, are always accompanied by the wild-type sequence of the second allele. Though many powerful techniques for genetic diagnosis have been developed over the past decade, all are compromised by the presence of diploidy in the template. For example, the presence of a wild-type band of the same electrophoretic mobility as a mutant band can complicate interpretation of sequencing ladders, especially when the mutant band is of lower intensity. Deletions of a segment of DNA are even more problematic, as in such cases only the wild-type allele is amplified and analyzed by standard techniques. These issues present difficulties for the diagnosis of monogenic diseases and are even more problematic for multigenic diseases, where causative mutations can occur in any of several different genes. Such multigenism is the rule rather than the exception for common predisposition syndromes, such as those associated with breast and colon cancer, blindness, and hematologic, neurological, and cardiovascular diseases. The sensitivity of genetic diagnostics for these diseases is currently suboptimal, with 30% to 70% of cases refractory to genetic analysis.
There is a need in the art for simply separating and analyzing individual alleles from human and other mammalian cells.